Harvey
Release status: Design
| Description | design of Harvey
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| License | unknown
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| Author | |
| Contributors | |
| Based-on | [[]]
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| Categories | |
| CAD Models | KiCAD
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| External Link |
Harvey is yet another reprap electronics / reprap controller Board. It is built around a STM32F102 Cortex M3 and uses Sanyo LV8549M Stepper Drivers, everything on one small PCB.
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Beware, this has not yet been assembled and tested. If anyone feels like checking the design, please do so. In #reprap I'm gnurbs, jabber mesages go to [email protected] |
Contents
Design
This Board was designed by ari, with his personal design conceptions: SMD-Parts where available, single sided, very compact single PCB. In fact it is so small, it will need a Heat spreader for the stepper drivers. Ari finds SMD-parts more convenient, especially if one produces the pcb oneself - less drilling.
Logic power (+3.3V) is supplied by USB, Power (VDD) by a 5.5/2.5 mm Jack. 8-16V are allowed, the actual voltage is measured by the µC. Up to 20V nothing will be fried but the steppers cannot be used. maybe add a fat diode for reverse voltage protection at the power jack. One of the IBM-thinkpad laptop power supplies should do. In the last sentence put emphasis on IBM as in not Lenovo. Those are 16V and have a fitting jack.
Definitions
| symbol | definition |
|---|---|
| Pex | expansion Header |
| Pprog | programming header |
Logic
This Board features an STM32F102 microcontroller. relevant for this Board:
- 48 MHz Cortex M3 core. Maybe upgrade to STM32F103C8T6 for 72MHz
- DMA
- builtin USB
- 2 Timers with 4 PWM channels each
- 12-bit ADC
programming header
Pprog is the programming header. You can flash the µC over USART1 when BOOT0 is asserted during reset. These plus USART1s clock are on the header. I think you could also use this as a second SPI
expansion header
This header is intended for future extension. It has all the unsused pins of the STM32, with several interfaces available:
- JTAG
- SPI
- I2C
- USART1
All but one Pin are 5V tolerant. Again PB5/Pex:8 is not 5V tolerant! Should you want to design a 5V Logiclevel expansion make absolutely sure not to use PB5.
maybe a board with lcd, sd-slot and some buttons would be nice to have as an expansion :D Ethernet, too
PWM Channels
I just thought I connected two pairs of stepper to the same PWM channel, so I'm listing all of them here B:=TIM2_CH, C:=TIM3_CH
| B3 | eEn |
| B4 | xEn |
| C2 | yEn |
| C1 | zEn |
| B1 | ePWM |
| B2 | bPWM |
Power
Stepper Drivers are Sanyo LV8549M which are pretty dumb but require no external parts. They are not much more than two H-bridges that are controlled by two pins setting the pase and one enable. Being H-Bridges they cannot do microstepping on their own, but doing this by hand should be possible. They have an enable-pin that is said to accept PWM for current setting, but the datasheet gives no details. They are wired to PWM-channels of the µC anyway.
Two PWM channels are wired to FETs (IRLML6344TRPbF with 29 mOhm R_ds(on), spec'ed to 1.3A, that gives 20W on each teater - that's a little little. However, they are also spec'ed to 0.8 W Power dissipation, which makes me think 4A could also be possible. Thinking about this, one should propably use other connectors for the heaters.
ToDo
connect Boot0 to Pex:11- done but to be reverted - I thought this could be used as GPIO when not in reset.put a cap between nRST and GNDrewire {bPWM,ePWM}^{eEn,xEn} -.-check if all pins on the expansion Header are 5V-tolerant.- PB5 is not
maybe +3.3, VDD and status LED would be nice.
